2025 is set to conclude as the second hottest year on record, following only the exceptionally warm year of 2024. According to the Copernicus Climate Change Service, this trend highlights a concerning pattern of unexplained global warming. The past three years have been the hottest ever documented, each exceeding 1.5 degrees Celsius above preindustrial levels. This situation temporarily breaches an international goal to limit warming to below that threshold.
The recent surge in temperatures has perplexed scientists, as it surpasses the predictions made by climate models. Researchers are investigating various potential factors, including a significant volcanic eruption in the South Pacific and a reduction in sunlight-blocking pollution. In an analysis published in Carbon Brief, climate scientist Zeke Hausfather examined four key drivers that might explain this warming trend.
Possible Factors Behind the Warming Surge
One significant contributor is the 2022 eruption of Hunga Tonga–Hunga Ha‘apai, which released a large plume of heat-trapping water vapor into the upper atmosphere. This volcanic activity coincides with the recent increase in global temperatures. However, Hausfather notes that these factors account for less than half of the overall temperature rise.
Another potential contributor is the increase in solar output. Although this aligns closely with the recent spike in warming, it does not fully explain the temperature rise observed in early 2023.
The formation of a powerful El Niño event in late 2023 also plays a role in the current climate scenario. This phenomenon, characterized by warmer waters in the eastern Pacific, typically drives up global temperatures. While it may explain the exceptional warmth of 2024, it cannot account for the earlier rise in temperatures.
The decline in emissions of sulfur dioxide presents another critical factor. This pollutant, primarily emitted by coal power plants, has a cooling effect by blocking sunlight. Over the past 18 years, sulfur dioxide emissions have dropped by 40 percent, largely due to efforts in countries like China to reduce coal burning pollution. Additionally, a new international regulation implemented in 2020 limited sulfur dioxide emissions from cargo ships, leading to a significant decrease in shipping-related pollution.
Research generally indicates that reductions in shipping pollution have had a modest effect on global temperatures. However, a study by James Hansen, the former chief climate scientist at NASA, suggests that this decline could account for nearly all of the recent exceptional warming.
Implications and Future Considerations
While Hausfather concludes that these four factors collectively may explain the recent temperature surge, he raises pressing questions about the implications of this warming. Is this phenomenon a temporary spike, or does it signal an acceleration in global warming trends?
The urgent nature of these inquiries reflects the growing concern among scientists and policymakers regarding climate change. As 2025 draws to a close, the implications of these findings will likely influence future climate policies and discussions on mitigating global warming.
As the world grapples with these challenges, the need for comprehensive strategies to address climate change becomes increasingly critical. The data reveals not only the immediate impacts of rising temperatures but also the long-term consequences for global ecosystems and human populations.
